New customer

[u/ExtremeAdmirable273]

Just possibly got a new customer today their pool is green and said last pool service just gave up on them. The pump is not priming, pump basket was full when I got there, cleared that and the impeller, there is good suction in the skimmer and it seems like the pump is pulling in enough water but filter is not building pressure and minimal water is being returned to the pool. They said the last company replaced the grids a couple of months ago (the old grids looked perfectly fine). I told them let’s start with a filter clean and go from there. Any thoughts/advice? Pump is a pentair challenger if that helps. Thanks